Internally heated cold manifold mold



June 22 1965 E. H. WHITNEY 3,189,948

INTERNALLY HEATED COLD MANIFOLD MOLD Filed Sept. 14, 1962 2 Sheets-Sheetl "HIM.

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INVENTOR. EDGAR H. WHITNEY BY @wm@ ATTORNEY.

June 22, 1965 E. H. WHITNEY 3,189,948

INTERNALLY HEATED COLD MANIFOLD MOLD Filed Sept. 14, 1962 2 Sheets-Sheet2 INVENTOR EDGAR H. WHITNEY ATTORNEY.

United States Patent 3,189,948 INTERNALLY HEATED CDLD MANIFQL-l)Mi'ifrl) Edgar H. Whitney, Dunellon, Fla, assignor to Osiey & Whitney,Inc., Westfield, Mass. Filed Sept. 14, 1962, Ser. No. 223,652 2 Claims.(Cl. 18-38) The present invention relates generally to new and usefulimprovements and structural refinements in an injection molding machineand more particularly in molds or dies therefor including means forheating the thermoplastic derivatives of cellulose and artificial resinsdelivered thereto and it is directed especially to the provision of suchmold-s or dies incorporating a cold manifold, and to an improvement in ameans for internally pedo or -pineapple") over which the body of moldingmaterial is adapted to tlow as a relatively thin annular or tubularstream, said molding material being plasticized by heat supplied fromthe surrounding cylinder and also from within the spreader, the materialthus heated and plasticized then being transformed from tubular form soas to flow as a rod-like stream for injection through an injectionnozzle into a suitable mold cavity.

Without intending to place undue limitations upon the scope of theinvention beyond what may be required by the state of the prior art, theparticular embodiment may be briefly described as a system forheating aplastic within a .cold manifold, having general utility in the arts.

It will be helpful to an understanding of the invention first toconsider briefly some of the more essential and important features andaspects of the prior art and of the present invention, so that same maybe kept in mind during subsequent reading 'of the detailed descriptionof the practical embodiment of my improvements and illustration thereofin the hereunto annexed drawings.

One of the inherent problems connected with the provision of aninjection cylinder assembly of the character referred to which has aninjection nozzle centrally located at one end is that the heatingelement in the spreader can only be assembled therein from the shankend, thus requiring a cap or plug or the like to be Welded to thespreader shank. In the event of burning out of said element, replacementthereof has been diilicult or impossible, and as a result, the operatormay elect to usethe machine with an unheated spreader in order to savethe cost of replacement of the entire spreader and heater assembly, butat the expense of a lengthened molding cycle and an inferior resultantproduct.

Another difficulty heretofore experienced results from leakage orcreeping of material into crevices between axially interfitting surfacesof the spreader and the mani fold body whereby such material chars orburns in such crevices so as to contaminate thematerial flowingtherepast. Furthermore, crevices, sharp corners, and the like in thepath of flow cause the material to hang up thereat, inducing non-uniformflow of the material as well as overheating thereof with con-sequentdecomposition in some instances and burning or charring with resultingcontamination. l a

The existing practice in the trade, asexemplified by the prior artconstructions of injection molding machines heretofore known, has beento provide electrically heated 3,189,948- l' atented June 22, 1965melting chambers with the outer'surfaces of the manifold being coveredwith suitably disposed heating bodies, which supply heat to such areaswhere needed. Melting chambers of this kind are particularlysuitable forvarious materials which are not sensitive to over-heating. The meltingchamber has to be designed for considerable pressures, required for thepressing or injecting of the material which is not always uniformlymelted and in numerous points remains in a relativelysolid state, as noprovision is known as yet by which a material which is molten in oneplace could be withdrawn irrespective of the condition of material inother portions. Moreover, in the known melting chambers, a considerablevolume of material, ready for melting, is contained, which fact mayeasily be a cause of decomposition of such thermoplastic substanceswhich do not withstand a higher temperature for a longer period of time,as is frequently the case for instance in injection molding of articleshaving a smaller volume than the size of the melting chamber.

It has been suggested to remove such drawbacks by employing steam or hotwater heating in which case overheated portions are avoided. Suchprocedure presents grave difiiculties however particularly when workingwith high temperatures, eg above 200 C., in consequence of the highpressures required in such case.

As is well understood, spreader elements are known which are inserted inthe manifold in order to assist in effecting a uniform and efiicientheating of the plastic material as it passes throu-glrthe pressurecylinder. To this end, the element is designed so as, in the firstplace, to provide an additional source of heat and, in the second place,to spread the material and thus renderit more susceptible to the heatingaction both of the element and of the manifold Walls.

Also as is understood, the plastic material is normally fed to themanifold by a series of small strokes of one or more pistons or by asingle long stroke of a piston. The charge of plastic must then beheated to become substantially uniformly fused for a rapid eje'cit-oninto a die. In practice, it is difficult, if not impossible to heat alarge charge without heating some parts of the charge for too long atime or producing an excessive temperature therein. Such over-heatingresults in premature setting of thermosetting materials or burning oftrue thermoplas-tics This has posed a problem which has not been solvedheretofore, to my knowledge. With thermosetting materials, the die isheated and imparts considerable heat to the heating cylinder by contacttherewith, thus aggravating the problem. It has been proposed toovercome this difiiculty by water cooling the injection nozzle of theheating cylinder, but this has been found to be unsatisfactory.

In prior art, it has been known to place heating cartridges on theoutside of the manifold Wherefore the entire manifold is heated, causingoverheating of the material with consequent loss of control thereoverand with the further results that excessive expansion and contractiontake place in the manifold as it is heated or cooled. In many instances,the expansion is so great that the nozzles leading to the moldcavitiesare broken or badly distorted, necessitating machine disasemblyand replacement of the damaged or broken parts.

With the conventional so-called hot runners in these prior artstructures, it is not possible to control and maintain different moldingtemperatures in different parts of the mold, so that overheatingand/or.underheatinghave produced vexing problems,

In other instances, heat is transmitted to the structure through theouter wall by electric heating coils mounted on the outside of saidwall. In order to achieve a proper heat transmission to the center ofthe plastic material, ribs are provided in the cylinder bore in such away that around the center a certain cross section remains unrestrictedso as to lower the resistance to flow. However, ribs arranged on theinner Wall are difiicult to manufacture. Moreover, the material in theunrestricted centrally located cross section is but poorly heated withthe result that this flow-temperature material mixes, on its travelthrough the cylinder, with other better heated material located betweenthe ribs. When this mixture with its heterogeneous temperatures isinjected through the nozzle, the quality of the moldings is not uniform.

These prior art constructions teach heated chambers, admittedly, but Iam also aware of a paucity of suitable instrumentation which has beenthe stimulus for these improvisations and I am further aware that, untilnow, no satisfactory construction has been forthcoming which combines ina simple manner the multiplicity of desirable features in a constructionof this type.

These prior constructions are thus attended with certain seriousdisadvantages and limitations which have militated against their moregeneral adaption.

In eontradistinotion, I have discovered that all of these difiicultiesand disadvantages are overcome and new advantages accrue when and as thestructure of my invention is employed.

I accomplish this by the provision of a device which obviates theaforesaid objectionable inconveniences.

The structure is diiferentiated from prior structures by numerousspecific characteristics which not only differentiate it from priorsimilar structures but which contribute essentially to its utility.

It is therefore a principal object of the invention to provide aninventively novel and improved construction of the type of injectioncylinder which enables thorough plasticization of the charge at lowertemperatures and in shorter periods of time whereby to preventoverheating and decomposition and to materially shorten the moldingcycle.

And it is another object of the invention to furnish an improvement inthe art which, on the basis of the factors involved, is capable ofsolving the diflieulties hereto-fore presented and of assuring thatplastic materials may be heated in an enclosed heating chamber ofrelatively large area and volume, the pressure being generated in andderived from a material feed and pressure channel in open communicationwith the heating chamber. The heating chamber leads to and communicateswith the mold cavity of the apparatus and the plastic material iscarried to the mold cavity under the pressure produced in the feed andpressure channel, the product being formed to the required shape in themold cavity. For thermosetting materials, the heating in the heatingchamber may be sufiiciently high in temperature for exothermic reactionto take place, and for the material to cure rapidly even though the moldcan be heated, whereby if desired the molded piece may be rapidlyejected from or through the mold cavity to permit final reaction to takeplace outside the mold.

For further comprehension of the invention, let it be stated that onegeneral object hereof is to provide an improved construction of aspreader element which is designed to otter a minimum resistance to theflow of rna-= terial through the passages which it forms within thecylinder and at the same time is sufi'icientiy strong to withstand therelatively high pressures, on the order of 30,000 lbs. per square inch,to which it is subjected in the pressure cylinder.

The present improvements, while retaining the advantageous features ofprevious constructions found in spreaders, provide, in addition, for thebetter incorporation therein of the necessary heating element and ofthermostatic means for controlling such heating element so as to insurethe uniform heating of the plastic material as it is injected from thepressure cylinder, and more importantly, I provide a system whereby, ina manifold, the molding temperatures in dilierent portions of the moldmay be individually controlled, same being accomplished by a systemcomprehending a cold manifold having heating means strategicallydisposed internally thereof, in the sprue channels or runners, with eachof the heating means being individually, and independently controlledwherefore complete temperature control is obtained in all sections ofthe manifold, making the mold etiective for use with crystallinetherm'opla'stics.

Another chief object of the present invention is the economic andexpeditious production of a manifold assembly including a heatingchamber for a plastic material extended under high pressure by aninjection molding device, especially of the piston .and cylinder type.

The objectional features referred to above as existing in the prior artare here overcome in the design hereof wherein heating elements areindividually controlled so as to allow complete temperature control inall sections of the manifold and are strategically located within therunners, with the result that the manifold remains rela tively cold atall times wherefore the possibility ofgrat distortion is precluded, itbeing appreciated that a cold manifold is the desideratum.

The invention possesses other objects and valuable features which are ofadvantage in other relations. For instance, I comprehend that a certainportion of thermoplastic material within the channels or runners of themanifold is heated to a fluid state while another portion thereofremains in a relatively solid state due to the contact with the coldmetal of the manifold. That is, a certain amount of the plastic masswithin a runner (say about remains relatively cold adjacent to its outerperimeter for the reason that the plastic mass is internally heated fromwithin wherefore the metal of the manifold takes such heat as isgenerated away so as to effectuate a tendency of the material tosolidify adjacent its outer periphery.

Still a further object hereof is .to reduce the length of the runners orsprues so that a more etficient use of the space within a manifold isenvisioned, while concomitantly the amount of plastic scrap formed inthe said runners or sprues between successive charges is eliminated. Byso disposing the heating elements in the runners, I am able to maintainthe plastic material in said runners in a molten state at all times,ready for subsequent use on the next machine cycle.

Too, by reducing the length of the runners, I have been able to increasethe number of cavities by as much as 30%.

More specific objects of the invention are:

'First: to provide .a new design for cold manifold molds of the abovementioned type particularly adapted for use with semi-crystallinethermoplastics which will offer a smoothness, ease and precision inassembly, handling and operation with the elimination of theconventional sprue and runners and the consequent problems incident tothe handling of rework.

Second: to provide a structure that permits of use with a minimum ofneed for rep-air or maintenance on the part of the user.

Third: to provide a construction of the aforedescri-bed type that willrequire but little attendance and that, by its large capacity andrapidity and accuracy of action will enable the user of the machine tomanufacture the finished articles cheaply and economically, with aminimization, if not complete elimination of the trimming of the moldedparts, all resulting in important distinct advantages in positiveness ofautomated operation and ease of manual control and action under thevarying conditions of practical use, and providing an increasedutilization of press capacity, an economy of manufacture, a capabilityof ready assembly and operation, and a reliability of performance.

Another object of the invention is the incorporation of theseadvantageous results mentioned above in a machine in which a reductionin fill time and a reduction in the sneasae time cycle of operation,particularly in the case of thin wall parts, is experienced.

One of the subsidiary objects of the invention is the achievement ofthese aforesaid desired results by. the use of a simple system of thetype above indicated.

In addition to the practical advantages which .I ascribe hereto, it willbe observable that another chief feature of the invention resides in thefact that a more uniform pressure and shrinkage in multi-cavity molds,is experienced.

Preferably, though not obligatorily, the invention envisions, as anotherobjective, a response to a survey of the industry which has suggestedthat a most important consideration is temperature control. The molddesign which I have developed embodies controls on each major section ofthe manifold as well as on each nozzle, along with powerstats foreffectuating a temperature control and longer heating cartridge life.

To make the manufacture of manifolds a more profitable undertaking, themechanism embodying the essence of the invention has been engineered inmanner as to be simple in its construction, thus expediting economicallarge-scale production and assembly, the usual complexity of componentshaving been so greatly reduced as to offer a compact designrepresentative of a fundamentally new concept in the combining andcoacting of interrelated parts.

Precision of relative dimensioning of parts as militates againstinexpensive manufacture, simplicity of maintenance and care, andconsistency of performance in practical use have been assiduously bornein mind in the development of the present invention.

Too, I provide a manifold of the above-mentioned character in whichruggedness and durability of construction are combined with simplicityand ease of use and protection against usual but hard conditions ofpractical use resulting in an apparatus which effectively meets thenormal requirements therefor and performs its functions in a practicaland dependable manner.

Further, while the components are uniquely compact, they arenevertheless readily accessible for maintenance and replacement purposeswith a consequent reduction in maintenance costs over related devicesheretofore known.

Other of the chief objects and purposes hereof are to provideadvantageous structural and operational features in a device of theclass to which reference has been made so as to offer an apparatushaving the following inherent meritorious characteristics: first,engineeringwise, a uniqueness in design of coating parts wherefor thecomponents are coordinated for facile assembly and, when once assembled,are positively and securely retained in op-erative relationship so as tobe not readily separable from each other, accidentally or otherwise;second, a susceptibility to easy installation, third, at high degree ofsafety in its use; fourth, a high degree of etficiency and dependabilityin its operational use; fifth, the securement of a higher degree ofaccuracy and greater degree of variety in the manner of work performedtherewith than has heretofore been possible withprior devices known inthe art; sixth, the attainment of a convenience of arrangen ent of partsand a flexibility or a capability of adjustment by which a large varietyof work can be produced by means of the same device; seventh, theprovision of a construction which is well adapted to Withstand the usageto which a manifold is odinarily subjected, and eighth, the provision ofsuch other improvements in and relating to manifolds of the type abovereferred to as are hereinafter described and claimed.

Further objects are to provide a manifold conformable to the desiderataof the preceding paragraph and offering specific improvements in itsvarious operating instrumentalities, which themselves are minimum innumber, so that it is simple and compact in accordance with the demandsand dcsires of manufacturers and purchasers alike and so as to providedistinct advantages in that it is distinctive in its appearance,practical in its value, durable in its organization, reliable in itsoperation, and efficient in its use.

These foregoing objects and other incidental ends and advantagescharacterize the device of the present invention, and distinguish itfrom previously known devices of a kindred nature.

The objects of the invention are susceptibleof attainment by use ofconstructions different in certain respects from that disclosed, such asminor changes and'variations in dimensions, shape, form,cooperation ofmaterial and/ or type of subassembly and accessory, all withoutdeparting from the underlying principles, salient features, scope andspirit thereof.

While all of these objects are attainable in the preferred and disclosedembodiment, it is to be understood that, by utilizing the invention onlyin certain of its aspects, certain of the objects may be attainedindividually or in sub-groups without necessarily attaining all of theobjects. That is, while the advantages of the invention as here outlinedare best realized when all of its features and instrumentalities arecombined, useful embodiments may be produced involving less than thewhole.

To the end of attaining these objects and advantages and othershereinafter reasonably appearing, it will be xplained that the inventionconsists substantially in the particular construction, configuration,dispostiion, relationship, combination and function of the organizationof coacting elements, components and instrumentalities of a manifold asexemplified in the following detailed disclosure wherein the aforestatedobjects will be in part obvious and apparent and will be in part morefully pointed out.

It will be apparent, however, that the specific physical embodimentdelineated, albeit the preferred exemplification, is only indicative ofbut one of the multiplicity of ways in and purposes for which theprinciples, of the invention may be employed. The invention reverted tois not restricted or confined to said embodiment and is not intended tobe exhaustive of, nor limiting of, the spirit or scope hereof. On thecontrary, it is merely exemplary and explanatory and is submitted as abest known structural embodiment for the purpose of illustrating theinvention, in accordance with the, patent statutes that others skilledin the art to which the invention pertains, may so fully understand theinvention, its principles and the application thereof, that they mayembody it and adapt it in numerous forms, each as may be best suited tothe conditions and requirements of any particular use. The disclosure isgiven with a view to illustrating and explaining the details ofconstruction and arrangement of parts and the precise nature of theprinciples of the invention and their embodiment for practical use.

The precise construction of the figures of the drawings need not beslavishly followed as, of course, the manifold may have to bemechanically varied or alternatively constructed or modified inaccordance with any specific use contemplated therefor. Such adaptationsand/ or alternative constructions and/ or modifications are intended tobe comprehended within the meaning and purview and range of equivalenceof the below subjoined claims, there being no intent to have thisinvention limited to or circumscribed by any specific details.

Many other advantages, features and additional objects of the presentinvention will become manifest to those versed in the art upon makingreference to the following detailed description forming a part of thisspecification, when read in conjunction with the illustrations in theaccompanying sheets of drawings, and the characteristic features which Iconsider to be novel herewith, as to its construction and organizationand as to its'methods of manufacture and operation, will be betterunderstood from a consideration thereof.

To enable others skilled in the art so fully to comprehend theunderlying features hereof that they may embody the same in the variousways contemplated by this invention, drawings depicting a preferredtypical construction have been annexed as parts of this disclosure, andin such drawings, like characters of reference denote correspondingparts through all the views of which:

FIG. 1 is a fragmentary top plan view of the internally heated coldmanifold of the invention, with the top plate removed;

FIG. 2 is an end elevational view, taken from the right as seen in FIG.1, with portions of the manifold having been broken away for purposes ofclarity;

FIG. 3 is a fragmentary exploded elevational view of the heating meansof the invention; and

FIG. 4 is a greatly enlarged, somewhat diagrammatic, sectional viewtaken through one of the heating means of the invention.

In this description and appended claims, various components and detailsthereof will be identified by specific names for purposes ofconvenience. Although specific terms and expressions are employed forpurposes of identifying various components, they are used in a genericand descriptive sense only, and are intended to be as generic in theirapplication as the art will permit. The phraseology or terminologyemployed is not for the purpose of limitation and it is not intended toexclude any reasonable equivalents of the features shown and describedor portions thereof. I

With continued reference now to the drawings, I have shown, in FIG. 1, apreferred embodiment of the apparatus constructed in accordance with theteachings of the invention in order that the general relation andutility of the manifold may be better understood.

I have shown in said FIG. 1, a manifold 10, with the top plate thereofremoved, for purposes of clarity. Same is of a type and constructionsuitable for incorporation in any conventional injection moldingmachine.

Manifold is disposed between a pair of spaced, parallel,longitudinally-extending supports 12 and 14, which, in turn, rest uponand are supported by an upper mold section 16 (see FIG. 2) whichfunctions in cooperative relationship with a lower mold section 18, inknown manner, with the upper and lower mold sections 16 and 18 being sointerrelated that the body is transversely divided along a plane so thatthe sections are partible to permit the ready insertion thereinto andremoval therefrom of operating components, as occasion may require, andof course, the ejection of molded pieces therefrom as by a standard orconventional instrumentality, such as a movable ram. Also, as known, themold sections 16 and 18 define therebetween a plurality of mold cavities20.

In the embodiment shown, such a cavity is depicted in the shape of aheel of a ladys shoe, but it will be understood that same is shown forpurposes of illustration only, the mold hereof being adapted tofabricate thermoplastic articles of a variety of sizes and shapes.

Said manifold 10 is additionally provided with a vertically-disposedinlet 22 located centrally of its upper planar surface, which inlet iscontinuous with and communicates with a horizontally-disposedtransversely-extending material feed and pressure channel 24 formedwithin said manifold 10 downwardly of said upper planar surface.

A pair of horizontally-disposed, longitudinally-extend-.

ing, axially-aligned oppositely-facing material feed and pressurechannels 28 and 30 lead from and communicate with material feed andpressure channel 24, adjacent one end thereof, and a pair ofhorizontally-disposed, longitudinally-extending axially-alignedoppositely-facing material feed and pressure channels 32 and 34 leadfrom and communicate with material feed and pressure channel 24,adjacent the opposite end thereof.

' Stated otherwise, material feed and pressure channels 28 and 32 aredisposed in coplanar relationship with channel 24 at one side of inlet22, and material feed and pressure channels 30 and 34 are disposed incoplanar relationship with channel 24 at the other side of inlet 22.

A plurality of spaced, vertically-extending material feed and pressurechannels 40 extend through manifold 10 and the upper mold section 16disposed therebelow, and are each disposed adjacent and in communicationwith one of the horizontal channels 24, 28, 3t 32, or 34.

Each channel 49 communicates with a mold cavity 20 defined between thesections 16 and 18.

As shown in FIG. 2, a top plate 44 surmounts manifold 10 in a mannerwherefore its opposite sides are seated upon supports 12 and 14, and aninlet funnel 46, extending through said top plate 44, is concentricallyrelated with and communicates with inlet 22 in the manifold.

The plastic material being operated on may be ejected under pressure ofa reciprocating plunger or the like and delivered in a series ofsuccessive charges through inlet funnel as and inlet 22 to material feedand pressure channel 24 and thence to each of the channels 23, 30, 32and 34, and thence through each of the respective vertically-disposedchannels 40, and therefrom into the respec tive mold cavity 29.

It will be understood and appreciated that the plastic material fiowabletherethrough comprehends thermoplastic material containing a derivativeof cellulose, such as the organic derivatives of cellulose, which may bean organic acid ester of cellulose, a cellulose ether, a mixed ester ofcellulose or a mixed ester-ether of cellulose. Examples of organicesters of cellulose are cellulose acetate, cellulose format cellulosepropionate and cellulose butyrate, while examples of cellulose ethersare methyl cellulose, ethyl cellulose and benzyl cellulose. Examples ofmixed esters of cellulose are cellulose nitro-acetate and celluloseacetate-propionate, while examples of mixed ester-ethers of celluloseare benzyl cellulose acetate and methyl cellulose acetate. Mixtures ofany of the above derivatives of cellulose may also be employed herein.

The walls of the manifold are made relatively heavy such that there isno tendency for the walls to expand and form fissures in the inner wallor conduit due to the extreme pressure from within or to buck from thestresses applied at the nozzle tips. Such fissures are formed unless thewalls are relatively thick and these fissures tend to hold for a periodof time material which would otherwise flow readily on through the mold.The material held in the fissures tends to decompose and corrodedmaterial may pass on into the mold, thus contaminating the article. Thecorroded material also tends to gradually enlarge the fissure until theassembly explodes at that part. Furthermore, the material held for aperiod of time in a fissure becomes overheated and in the molded articleforms a brittle spot.

A heating element 35 is disposed in each of the aforementioned channels28, 30, 32 and 34 and a heating element 36' is disposed in channel 22.Similarly, each channel 40 has a heating element 42 disposed therein,with all heating elements cooperatively functioning to maintain theplastic material in the desired molten or flowable state over a certainarea thereof.

Said heating elements form a network which is connected to a centralcontrol panel (not shown), inclusive of powerst-ats or the like, wherebythe heating of each said heating element may be individually controlled.

The heating elements 36 are identical in configuration and eachcomprises an outer cylindrical shank portion 50, the outer diameter ofwhich is smaller than the diameter of the respective channel in which itis receivable and a head portion 52 of increased diameter adjacent oneend thereof. Said head portion has an outermost threaded annular portionand is of substantially the same diameter as its respective channel soas to be threadedly fitted therewithin. At the opposite end of theheating element, a plurality of radially outwardly-extending lugs orribs or projections 54 are provided in order to retain such end andshank portions as a whole in proper concentric relation to its chanel.The end surfaces of the lugs or ribs and the inner wall surface of thechannel are ground :so as to form a fluid-tight.metal-to-met-al jointthereat, as to accurately locate the shank of the element 36 centrallywithin the bore. As apparent, said ribs alternatively may beprovided onthe. inner wall of the bore.

As is common, the inner end .of the heating element may be of bulletshape or prolate form. t

A removable electrical heating unit in the form of a cylindricalcartridge .56ofany one of a number of wellknown commercially availabletypes is insertable into the core of the shank portion '50 so as to besnugly and replaceably receivable therein.

The shank portion 50 known in .the trade a torpedo, with the cantridge56disposed therein, as in turn .insertable into its respective channel 28,30, 32, or 34. For purposes of illustration only, shank portion 50 isshown as being associated with channel 28, .in FIG. 3.

As aforesaid, the shank portion 50 is of a smaller diameter than that ofthe channel 28 in order that the plasticmaterial may flow therearoundand Within the channel.

The heating cartridges. 56'hereof have longitudinallyextending leadwires 58 imbedded therein and extending outwardly from an end thereof,said lead wires being suitably connected to a powerstatprovided in asuitable control panel (not shown) wherefore the electric currentsupplied to the heating unit may be automatically varied so thatthe-discharged material will be at the right temperature for the moldingoperation.

The constructionof theelements 36, furthermore, is suchthat-access maybereadily had to such heating cartridges 56 without removingthe entireelementfrom the manifold, all whereby repair and maintenance of theelements is facilitated.

Heating element 36', disposed in channel 24,is identical in all respectswith the elements 36, with the exception that the ribs or projections 54have been omitted from the innermost end of shank portion 50. Channel24, having a relatively short run, and heating element 36, consequently,being of relatively short length, the support provided by theprojections 54 is not required in the case of element 36'.

The heating elements 42 disposed within the vertical channels 40 differsomewhat in construction from that described with reference to theheating elements 36 and 36', and are associated with nozzle means fordirecting the plastic material disposed in channels 40 into the moldcavities 20.

As shown in FIGS. 2 and 3, each heating element 42 comprises a shankportion torpedo 60 provided with a threaded shoulder 62 at one end andhaving disposed therein a heating cartridge 64, carrying heating wires66. The heating wires 66 of each cartridge are connected to a powerstatfor heat control purposes, as previously described.

The free end of the torpedo 60 is receivable in the bore of a shell ornozzle 70 threaded in the channel 40 and having a spout 72 opening intoone of the cavities 20.

Ejector pins 74 extend transversely through appropriate openingsprovided in the mold 16 for the purpose of ejecting the finished partfrom the mold cavity in knownmanner.

The ejector pins will preferably be linked so as to be operablesimultaneously by suitable power means. Same not forming any part of thepresent invention, further discussion thereof will not be made.

With particular reference to FIG. 4, plastic material 88 is shown forpurposes of illustration, as flowing in a molten state immediatelyadjacent heating element 36 disposed in channel 28. This area of moltenplastic is designated by the letter a in FIG. 4. However, in that areaof the plastic material removed from contact with the heating element,the plastic material is less fluid, being at a lower temperature. Thisarea is designated by the letter b in FIG. 4. Finally, that portion ofthe plastic material which is in contact with the relatively cold wallof channel 28 approaches the solid state.

tion only.

The material will, in fact, gradually go from a fluid state adjacent theheating means, to an almost solid state adjacent the relatively coldmanifold.

Experience has shown that the lowest melting point of most thermoplasticmaterials is approximately 400. The temperature of the plastic isapproximately wherefore it is actually in a solid state.

Thus, the manifold remains cold at all times wherefore the possibilityof distortion therein due to constant expansion and contraction isobviated, and the possibility of damage tothe nozzles is greatlydiminished.

The flow of the plasticmaterial 80, in the mold hereof, will be throughthe inlet funnel 46 and the inlet opening 22 and into the channels 24,28, 30, 32 and 34 where it is heated by the heating elements 36' and 36,respectively (it being understood that the plastic material is disposedbetween the shank portion or torpedo of the heating element and the wallof the channel and flows between the ribs 54 of the shank portion in thecase of elements 36), and into the vertical runners 40, where it isheated by the heating elements 42 and fed into the cavities 20 by thenozzles 70.

From the above, it will be apparent that the plastic material is heatedat all times after it enters the mold, and at no time is it allowed tosolidify completely.

By this means, the problem of excess scrap occasioned by solidifiedplastic material in long sprue channels is solved.

By means of the novel system and constructions hereof, there isvirtually no scrap, resulting in tremendous savings in down timerequired to remove the solidified material from the runners forreclaiming by being reground, etc.

Other modes of applying the principle of my invention may be employedinstead of the one explained, change being made as regards the mechanismherein disclosed, provided the means stated by any of the followingclaims or the equivalent of such stated means be employed.

.It is believed that the gist of the invention will be clearlyunderstood from the foregoing disclosure and accordingly, furtheranalysis thereof at this point is considered unnecessary, as I have, inaccordance with the provisions of the patent statutes, described theconstruction and principle of operation of my invention together withthe apparatus which I believe to represent the best embodiment thereof,to the end that others can, by applying current knowledge, readily adaptit for various applications without omitting features which, from thestandpoint of prior art, fairly constitute essential characteristics ofits generic and/ or specific aspects. The substitution of equivalentsand other changes, modifications and alterations as circumstances maysuggest or render expedient, are reasonably contemplated, the inventionbeing susceptible of such without departing from its real spirit orunderlying principles.

The claims are desired to include within the scope thereof all of saidsuitable variations, modifications and equivalents by whichsubstantially the results of the invention may be obtained, through theuse of substantially the same or equivalent devices or means.Accordingly, limitation hereof should only be made as determined by aproper interpretation of the prior art and the scope of the subjoinedclaims, in which it is my intention to claim all novelty inherent hereinas broadly as possible.

I therefore particularly point out and distinctly claim as my invention:

1. In a mold having partible mold sections defining a plurality ofcavities therebetween for receipt of thermoplastic material therein, aninternally heated. cold manifold mounted on one of the mold sections andhaving horizontally-extending and vertically-extending interconnectingchannels in said manifold forming an interconnected network, thevertically-extending channel being offset relative to the respectiveinterconnected horizontallyextending channel, an inlet opening in saidmanifold communicating with at least one of said channels, heatingelements extending into each of said channels from the mold exterior,the heating elements disposed in said horizontally-extending channelscomprising a heating cartridge sleeved by a metal sheath threadedlyengaged in said channels and having a plurality of radial ribs embracingthe walls of said channels, nozzles in said vertically-disposedchannelsopening into said cavities, the heating elements disposed insaid vertically-extending channels comprising a heating cartridgesleeved by a metal sheath threadedly engaged at one end in one of saidchannels and sleeved at its opposite end by one of said nozzles, andtemperature control means for each of said heating elements whereby thetemperature of the thermoplastic material in the cavities of the moldand in said channels of the manifold may be individually controlled.

2. In a mold having partible mold sections defining a plurality ofcavities therebetween for receipt of thermoplastic material therein, thecombination of, an internallyheated cold manifold mounted on one of thepartible mold sections and having horizontally-extending andvertically-extending interconnecting channels forming an interconnectednetwork, the vertically-extending channels being offset from therespective interconnecting horizontally-extending channels, an inletopening in said manifold communicating with at least one of theinterconnecting channels, a heating element extending into each of theinterconnecting channels from the mold exterior, the heating elementdisposed in each horizontally-extending channel comprising a heatingcartridge sleeved by a metal sheath threadedly engaged in the respectivechannel and having a plurality of radial ribs embracing the walls of therespective channel, a nozzle disposed in each vertically-disposedchannel and opening into one of the cavities, the heating elementdisposed in each verticallyextending channel comprising a heatingcartridge sleeved by a metal sheath threadedly engaged at one end in therespective channel and sleeved at its opposite end by the respectivesaid nozzle, and a temperature control means for each said heatingelement whereby the temperature of the thermoplastic material in thecavities of the mold and in the interconnecting channels of saidmanifold may be individually controlled.

References tilted by the Examiner UNITED STATES PATENTS I. SPENCEROVERHOLSER, Primary Examiner. MICHAEL V. BRINDISI, Examiner.

1. IN A MOLD HAVING PARTIBLE MOLD SECTIONS DEFINING A PLURALITY OF CAVITIES THEREBETWEEN FOR RECEIPT OF THERMOPLASTIC MATERIAL THEREIN, AN INTERNALLY HEATED COLD MANIFOLD MOUNTED ON ONE OF THE MOLD SECTIONS AND HAVING HORIZONTALLY-EXTENDING AND VERTICALLY-EXTENDING INTERCONNECTING CHANNELS IN SAID MANIFOLD FORMING AN INTERCONNECTED NETWORK, THE VERTICALLY-EXTENDING CHANNEL BEING OFFSET RELATIVE TO THE RESPECTIVE INTERCONNECTED HORIZONTALLYEXTENDING CHANNEL, AN INLET OPENING IN SAID MANIFOLD COMMUNICATING WITH AT LEAST ONE OF SAID CHANNELS, HEATING ELEMENTS EXTENDING INTO EACH OF SAID CHANNELS FROM THE MOLD EXTERIOR, THE HEATING ELEMENTS DISPOSED IN SAID HORIZONTALLY-EXTENDING CHANNELS COMPRISING A HEATING CARTRIDGE SLEEVED BY A METAL SHEATH THREADEDLY ENGAGED IN SAID CHANNELS AND HAVING A PLURALITY OF RADIAL RIBS EMBRACING THE WALLS OF SAID CHANNELS, NOZZLES IN SAID VERTICALLY-DISPOSED CHANNELS OPENING INTO SAID CAVITIES, THE HEATING ELEMENTS DISPOSED IN SAID VERTICALLY-EXTENDING CHANNELS COMPRISING A HEATING CARTRIDGE SLEEVED BY A METAL SHEATH THREADEDLY ENGAGED AT ONE END IN ONE OF SAID CHANNELS AND SLEEVED AT ITS OPPOSITE END BY ONE OF SAID NOZZLES, AND TEMPERATURE CONTROL MEANS FOR EACH OF SAID HEATING ELEMENTS WHEREBY THE TEMPERATURE OF THE THERMOPLASTIC MATERIAL IN THE CAVITIES OF THE MOLD AND IN SAID CHANNELS OF THE MANIFOLD MAY BE INDIVIDUALLY CONTROLLED. 